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(No Model.) 2 Sheets-Sheet 2. B. A. FISKE.

-TELESCOPIG SIGHT. A No. 561,383. VPartentcedJune 2,1896.

.mwnmwm u i lwww UNITED STATES BRADLEY A. FISHE, OF THE PATENT UFEI'CE.

UNITED S"TES NAV-Y. I

TELESCOPC SIGHT.

SPECIFICATION forming' pari; of Letters :Patent NO. 561,383, 'dated June2, 1896. Application'led May 20. 1893. Serial No. 474,872. (No model.)

To all whom it mag/.concerm 13e it known that I,- BRADLEY A. FISKE, of-

the United States Navy, have invented a new and useful Improvement inTelescopic Sights, of which the following is a specification.

My invention relates -to an apparatus for sighting guns.

My invention consists in the combination of a telescope orsi ght-bar anda gun,each movable about a transverse horizontal axis, and means forindicating the angle in a vertical plane between the longitudinal axesof said telescope and gun; also in apparatus for electrically indicatingsaid angle; also in apparatus for compensating for the error in the lineof sight dueto the bodily movement of the gun, the target, or both; alsoin apparatus for compensating for the drift of the projectile when thegun is rifled; also in the various instrumentalities and combinations,mechanical and electrical, as hereinafter set fortl1,and moreparticularly pointed out in the claims.

In the accompanying drawings, Figure l. is a side elevation of my deviceapplied to a ships gun. Fig. 2 is a rear elevation of the gun. to myapparatus for the purpose of supplying a correction to compensate forthemovement of either the ship or the target. Fig. i is an end elevationthereof. V Fig. is a detail view ofthe drum of insulating materialrepresented at 18 in Fig. 1. trical diagram illustrating the connectionsin the apparatus.

Similar letters and Iigurc's of reference indicate like part-s.

1 .represents so much of an ordinary naval gun as ,is necessary toillust ate the application of my device thereto.

2 is the gun-carriage.

3 is the gun-shield. On one side ot' said shield there is a shelf orledge 4, upon which my telescopic sight is supported. I

5 is an ordinary telescope or spy-glass, preferably providedwith-eross-hairs in its objec- -tive for the purpose of more accuratelybrin ging the line of sight upon the target. The telescope is mounted intrunnions 1l in the standard 6., Journaled in the standard C is ashaft', which carries a worm-wheel 8, and which on its outer end isprovided with a hand-wheel 0. 'lhe telescope carries the Fig. 3 is aplan View of an attachment` Fig. G is an elec-- however, there is hereshown a rack lil, connected to the gun, with which a pinion 1l cn-`gages. ]:ly turning the pinion ll by means of any suitable crank-handlethe gun may be elevated and depressed as desired. Of cou rse thisarrangement of rack and pinion 13 li is no part of my invention,inasmuch as the gun to which my device is attached may be elcvated ordepressed by any suitable means.

Connected to the carriage 2 by means of the arm l5 is an lare 1U*. Thisare carries astrip of wire 1G or other conducting material, insulatedfrom it. l, 17 is a contact-point of metal which is fastened upon thegun, but. insulated therefrom, and which bears against the wire 1G. vThe are 16* is struck. from the trnnnion 12.0f the gun asa center., sothat .when the breech oi' the gun is raised or lowered the contact-point17 always bea-rs against said wire lo, the arc moving, of course,'infront of the contactpoint., The shaft 7 is made in two parts 7 -and 7,as shown in; Fig. 5, and these parts terminate in a drum 18, of hardrubber or other insulatingmaterial. In the periphery of the drum 1Siscut a spiral thread, and in this thread is laid a strip of metal orwire 19, which exactly corresponds to the wire 1G in its resistance fromend to end. Of course this could bc produced by making the wire 19precisely similar to the wire 1U in point of material, cross-section,and length.

. 2O is a eontact-arm which slides freely upon a rod 21, 'whichis'supportcd in the insulated bracke 22 upon the table 23`of theappara-` tus. The contact-arm may be provided with a point, as shown inFig. 5, which point 'always bears upon the wire 1'9. n .Consequentlyas'the whe'el 9, and hence the shaft 7, is rotated the arm 20 remains inthe spiral groove of the drum 18, and of course follows that groove,this movement being permitted by the sliding oi the arm SO upenits rodor support For example,

A variety of same points on the respec'tive arc-wiresv 16 21.Therefore'eontaet between the arm 20 and the resistance-wire 19 isalways maintained.

As best shown in Fig. 5, the ends of the Wire 19 on the drum 18 areconnected, respectively, to insulated sleeves 19X on the sections 7 and7b of the shaft 7. Secured upon the table 22 are two insulatedcontact-springs 24 25, and these bear, respectively, upon said insulatedsleeves'. y

I will now describe the electrical connections in the apparatus. Fromthe end fl' of the wire 16 a wire 26 extends to the contactspring 25.From the en'd c of the wire 16 a wire27 extends to the contact spring 2Between the points and y of the wires 26 and 27 extends a wire 28,Awhich includes a battery 29. From the bracket which supports the arm20, which bears on the wire 1.9 in the drum 1S, extends a wire 30 to agalvanometer 31.. From the galvanometer 31 extends another wire 32 tothecontactspoint 17. The relation of these connections will be moreconveniently traced on l[he skeleton diagram,` Fig. 6. rlhis. diagram,as is obvious on inspection, represents the connections in thewell-known Vheatstone-bridge relation; and here it will be obvious thatwhen either of the are-wires 16 or 19 is moved al'ongthe contacts or 17,or, what is the same thing, if the contacts 2() or 17 be moved over thearc'- wires 19 or 16 the arms of the bridge will be lengthened orshortened, or, in other words, the resistances balanced in the bridgewill be varied, and hence its equilibrium will be disturbed.

Now supposing that in Fig. 6 the parts marked 20 and 17 being thecontact-points, are pivoted arms so arranged as to sweep over thearc-wires 16 and 1S), when these arms 20 and 17 stand parallel, touchingthe and 1f), clearly then the bridge willl balance and the galvanometer3l will give no deection. moved so that its end meets the are-wire 19,

lf, however, the supposed arm 20 be at the point 2i of that wire, then,clearly, We

lhave lengthencd the'arm w24 of the bridge and shortened the-arm if",a-nd the bridge will then be thrown out of equilibrium and thegalvanometer 31 will indicate the extent of this disturbance, which willof' course depend upon the resistance of the length of the wire 1f)included between' the original position of the arm 2() (full lines) andits new position. (Indicated by dotted lines.) Now, as the arc-wire 16is assumed to be exactly like the arc-wire 1f) in point of resistanceper unit length, and afs the electromotive force of the battery is, alsoassumed to be constant,

plainly if we move the supposed arm 17 to over an equal distance ofthe'fixed arc-wire 16,'or, in other words, to the point (l on thatarc-wire, then the remaining` arms of the bridge will become,respectively, yd and dr, or, in other words, we shall have compensatedfor the disturbance `in the bridge made by the movement ot' thesupposed-pivoted arm 20, and therefore the galvanolneter 3l will oncemore balance. The net result of all this is simply to show that thegalvanometer 31 will always indicate zero whenever the two supposedpivoted. arms 2O and 17 are placed on corresponding points of theirarc-v wires 16 and lJ-that is to say, whenever they are relativelyparallel one t0 the otherbut Whenever they are not parallel then thegalvanometer 31-will give a deflection which is proportional to thelength of are-wire which isincluded between .the angle which they bearone to the other. Thus, if the arm 17 is left as shown in full linesandthe arm 2O be moved to make Contact at 24;, as shown bydotted lines,then the galvauoineter 31 will give a deflect-ion due to the .resistanceincluded between the two positions of the arm 20. 0f course exactly thesame thing would happen if the arms 2O and 17 of Fig. 'l 6, heresupposed to be movable, were fixed and the arc-wires 16 and 19 weremoved in front of the arms. v

Returning now to Fig. 1, it will be plain that when we rotate the wheelQwe `move the wire 19 on the drum 1S beneath the couta-et-point 20, andat the same time by mea-ns of theworm S and rack 10 we turn the tele'-scope 5 on its trunnions. Y Therefore there is a relation between thelength of wire which passes beneath the contact-point 2O and the angleover which the telescope 5 is turned.

Similarly when we elevate or depress the gun, which likewise turns itupon its trunnions 12, we at4 the saine time move the arc-wire 16 infront-ot the contact-point 17, so that there. is a relation between theextent of .angular elevation or depression ot" the gun and the length ofthe arc-wire 16 which moves in Contact with the point 17. Now if theseparts be so adjusted, as in fact they are, that when the telescope 5- iselevated or depressed over a certain angle and the contact-point 2Otherefore moves over a certain length of the wire 19, the gun, on beingdepressed or elevated over that same angle, will cause an equalvlength-of the arc-wire 16 to move in front of the contact-point 17.

Then clearly we shall have between the axis of the telescope and theaxis ot' 'the gun the saine relations, with reference to the arewires 16and 1f), as have the two supposed pivoted arms 17 and 20 in the diagram,Fig.

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(i. The shelf i is so placed on the shield that y when the axis of thebo're of the gun and the line of sight of the telescope are .parallelone tothe other the contact-points 17 and 20 will stand on the sainerelative positions to their respective 'resistance-wires 16 and 19', andthe galvanometer 31 will show no deflection, so that thus we haveeverat'tera means ot knowing, by the indication of the' galvanometerbeing zero, when the l'ine ofI sight of the telescope and the axis ot'the bore of the gun are relatively parallel. Of course these connectionsin practice. are adjusted once for all, and, therefore theuse of thedevice becomes,

in fact, exceedingly simple, for all that the observer has to do if thegalvanometer .3l shows any deflection at all is to move either' gun ortelescope on its trunnions until the Agalvanoineter shows no deflection,and then he knows that gun and telescope are parallel.

The relations of the parts now being established, I will explain theirpractical use. In order to make the projectile thrown by a gun reach itstarget, it is necessary to elevate the gun over a certain angle(dependent upon the distance of the target) above the line of sightdrawn from the observers eye to the target; This distance may bedetermined by means of a range-finder or other apparatus especiallyadapted for that purpose, and the ordinary proceeding is, after therange has been determined or estimated, to suitably adjust a sight-baron the gun, so that a notch in the upper part of this bar and a fixedprojecting point or front sight at a distance therefrom along the gunshall be at a known angle tothe axis of the bore equal to the requisiteangle of elevation ofthe gun. 'lhe observer ranges his eye so as to notethe instant when these twoA points come into coineide'neewith thetarget, and then he lires the gun by any suitable means. Now oir-boardship this is a matter of consi deral )le difficulty and requires longtraining on the part of the person who is to direct the gun. It is anexceedingly diiiicult matter, especially when the ,.'hip ismoving, tocatch the instantwhen `the sights and object come into alinenient'-,

because the pupil of the eye must be kept exactly on the line producedjoining the front and the rearsights. lVha-t I accomplish in thispresent device is greatly to increase the accuracy and rapidity withwhich the sighting of the gun can be accomplished. This will be apparentfrom the `following description: For all practical purposes the axis ofthe telescope', when parallel with the axis of thebo'rc of the gun, maybe considered as coincident. In other words, the displacement of theaxis of the telescope above or laterally to the axis of the bore oi' thegun is so small with reference to the distance, over which the shot isthrown that any error due thereto may be neglected altogether. Assuming,For convenience, that in the beginning both giin and telescope standparallel to the. plane ofv the deck, as shown in Fig. l, thegalvanometer I3] then giving no deflection, the telescope 5 is broughttoybear upon the object, so that the object comes at the intersection ofits crosshairs. The necessary elevation to be given to the-gun, havingbeen determined by the ran ge'jlinder, is known Corresponding thereto isa certain deflection of the galvanometer 31. 'lhe needle inust goto acertain point on the galvanometer-scale corresponding to the extent towhich the bridge will' be thrown out of equilibrium by the knownanddesired elevationof the gun. Instead of marking the galvanometer 3lfor differences of potential dependent upon these changeait may as wellbe marked for yards correspondingto the po` needle shows that range, andthis he does by the ordinary elevating or lowering apparatus of the gun.IVhen the galvanometer-needle does show that range, then he knows thatthe nrun is adjusted with regard to the line of sight alreadyestablished at the proper angle to throw its shot over that distance. Ofcourse in practice these observations are notv made by one man. Oneobserver standing at the telescope and having in his hand ,thefiring-button directs the telescope upon the object. An assistantoperates the gun-elevatin g apparatus and watches the galvanonieter. Allthat the first operator has to do is to direct the telescope properly,and all that the second operator has to do is to elevate or depress thegun until the galvan oineter-ncedle indicates the desiredrange. lVhenthat range is reached, the first operator fires the gun soon as therolling ol? the ship brings the cross-hairs on the target. The iirstoperator has nothing to do with the elevation of the gun or itsadjustment for range. IIe maynot even know what the range is. The secondoperator has nothing to do with the sighting of the gun and cannot knowwhen the gun bears on the. object. justment of sights ,orI inaccuraeyinalinenient of sights and object arepraetically obviated.

I new pass toanothcrpart ofmy invention, i

which consists in a meanswhich serves the double purpose ol verifyingthe accuracy oi 4the galvanometer reading and also of accomplishing thesaine results alrcadystated by mechanical means in case ot any injuryvto the electrical connections.l On the tace of the wheel E) (see Fig.2) l make graduations and arrange in proximity to said wheel anindicating-point 33. Aswill readily be understood, by means of thesegraduations, which may be, say, in` degrees, I -can indicate the extentof elevationor depression of the tele- All errors from maladlOO scope 5.-I also attach to the gun a graduated are Si, the graduations onwhichcorrespond exactly to the graduations on wheel i). i On the arm 15 is aprojection 35, which is parallel to the graduated are 84, 'and thisprojection may be likewis'egraduated in the saine units as the are 34.Now-the'relatior-i of 'the graduations on the wheel '9 and the fixed arc34 on the gun are to be suoli that when the axis of the telescopeisfparallel vto theaxis ot `the bore of`,tl1e-gun'the saine"lgraduationmark on the wheel 9 which comes oppositethe 'pointer 33 willbe the saine as the grad-uation-mark on 'the arc 34 which cornes oppo-lThis For site the zero-point on the projection 35: zero-point may belocated as desired.

convenience I have shown it as being slibstantially the horizontal loweredge of the `arm. l5 between the part which carries the jection 35 isalso graduated, it is clear that by this means the angle between gun andtelescope can be easily read. For example, if the reading of the wheel 9is thrcedegrees and the two-degree mark ou the projection 35 is oppositethe three-degree mark on the arc 34, then it is clear that the bore ofthe gun is inclined at an angle of two degrees to the telescope, and,similarly, if the' reading of the wheel i) is three degrees and theone-degree mark on the projection is opposite the tl'iree-degree mark onthe arc 34, then the gun is inclined at an angle of one degree to thetelescope, so that by means of these graduations on the wheel 9, the areBt, and the projection 35 it becomes easy to give the gun and telescopeany relative angular convergence that may be desired. v In this wayalso, clearly, these graduations give a check to the indications ot' thegalvanolneter 3l, because, whatever may be the position of the telescopeand gun, the

- mark on the projection 35 which is opposite to that mark on the arc 34corresponding to the reading of the wheel should be the same as theindication in similar units of the galvanometer 3l, so that, further,even supposing all the electrical connections to -be destroyed, the gunand telescope can be laid parallel and the gun laid at any angle withreference to the telescope simply by observing the relation of thegraduations -on the parts named. 0f course in practice the electricalapparatus is `much vmore rapid, and in other respects preferable but thevalue of the last-described arrangement as a check on the galvanometerand as a means of meeting casualties in action will be readilyappreciated. 0f course instead of graduating 35 in degrees it may begraduated in yards' or meters once for all, because for any given gun,as already stated, the distance to which the shot Will go Ais entirelydependent upon the angular elevation of the muz` zle above the line ofsight from gun to target. I now pass to another part of myin vention,

which consists in means for applying to the apparatus a correction forrelative movement This of course involves p of gun and target. thefollowing conditions; Either the target is fixed and the gun is movable,as in the case ,when the ship which carries the gun is under way, or thegun is fixed and the target is moving, which is the condition when theship which carries the gun is stationary and tires, for example, at amovingship, and, third, when both the ship which carries the gun and thetarget which is fired at are moving one relatively t0 the other. 0fcourse in both lthe flrst and last cases the projectile will have notmcreljr the velocitydue toits `impelling charge, but also the velocityot' the ship, acting in a different direction and tending to carry it inadvance ofl the point aimed at. ln the second case, when the target ismoving, the projectile will tend to fall in rear of the point aimed at.A single illustration will suice to make this clear. if, as in Fig. 7,the ship A fires at the ship l, and meanwhile advances to A', the shotwill not strike B, but D, the distance l; D being merely equal to the4distai'icc A A', so that the gun must in fact be pointed not directlyat ll, but at an angle represented by l A C if rom the line of sight A lequal to the angle l) A l. This angle can be easily deduced for any andall speeds of ships, the speed or velocit y of the shot being known. Infact, itis always now deduced for everygun on board ship for use in,say, the ordinary sights, and it is usually called the correction forspeed. The same is truc for the correction of the speed of the othership 3, bearing in mind, of, course, that the correction must bein theopposite sense. I compensate 'for this in the following manner, (seeFigs. 3 and riz) The base 22 of the instrument is secured to the shelfl. en the gunshield 3 by means of a strong vertical holt 3G, about whichthe table Q2 may berotated as on a pivot. In the table Q2 is cut arectangular opening 3T, and on the shelf i there is a pin 258, havingone side flat and the other side curved, which projects up through thisopening. On the plate is a xed pin Si), and between the pins 3U 39 isinterposed the bent spring 40. On the plate 22 is also a threadedsupport 4l, which receives the adwhich is provided with a graduated head43. 'lhe end of the screw 42 bears against the flat side of the pin 3S.YWhen 43, the table or base-plate will be rotated around the pivot 3G,the spring i() acting in opposition to thc screw 2, so that thisadjustment maybe mad-e in either direction. It is also clear that if thepitch of the screw 42' be known and the head 4:3 be appropriately grad-vuated the telescope 5, which is supported on the base-plate 22, may beturned to any desired angle by simply rotating the head 1S and notingthe graduation. angle is seldom, if ever, as great asftwo degrecs,sothat thc construction dcscri hed abundantly provides for this necessarylimited extent of movement. It willbc readily under In practice this IOOthe screw 42 is turned by means oi its head IIO stood that by this meansthetelescope may be moved in azimuth to compensate for thel displacementoi' ci'lher the target or the ship which carries the jun. It is alsoplain that the microm-eter-head can be at once marked in units of speedinstead ot' in degrees and minutes of ar'c.

There is also another small, but important,- correction necessitated bywhat is termed in gunnerythe drift of a projectile when .ired from ariled gun, this drift being a deviation from the line of fire to theright or the left, a right-handed riiiing causing the projectile tdeviate to the right and aloft-handed ri fi ing causing the projectileto deviate toward the left. The distance to the right or left to whichthe shot is thus deviated increases with the distance to which the shotis fired, and it becomes necessary, therefore, to apply a correctionwhich also increases' with the distance to which the shot is fired.lVith the ordinary sight-bar this correction is accomplished by placingthe support of each sight-bar t one side of aline parallel to the boreofthe gun from the front sight and by inclining it at an angle, so' thatthe rear sight-bar as it is raised does not rise in arvertical plane,but in one at an angle thereto. In my present device I provide for thiscorrection in the followingl manner: Upon the base-plate 22 andin'proximity to the graduated head 43 is supported a small iixedgraduated arc 44, which is graduated in degrees and minutes of arcorpret'- erably in terms of the ranges corresponding to these angles ofdrift. l In the ordinary use of a micrometer thercading is that of thegraduation:D on the micrometerhead, such ris-13, which is opposite to acertain fixed zero or reference mark. In using the micrometerhead 43 Ibring thc speed-graduation thereon opposite to the zero-mark on 44 inthe supposititious case where the distance of the target is zero; but asthe distance is of course not zero I bring the spoed-mark on 43 oppositeto the graduation-mark on 44 which corresponds to the distance of thetarget. In case, for example, the speed of the ship were ten knots andthe dista-nee of the target tiftcen hundred Yyards I bring the mark 10"on 43 opposite the mark 1500 on 44 5 and in ease the distance is twothousand yards and the speed zero, as when the iilrin g ship is atanchor an d the target stationary or when both are going in the samedirection at equal speeds, I bring the zero -mark on 43 opposite the200()77 mark on 44. Of course the relations of these parts depend uponknown determinassv tions with which all persons skilled in the art arefully familiar and which need no description here, so that it is evidentby this arrangement I am able,quickly and conveniently and withsufficient accuracy, to make at the same time the two corrections forspeed and drift.

I claimo 1. The combination of the gun 1, movable on a transverse,horizontal axis, the elongated body 16 of conducting material andcontactarm 17, the said body 16 .and arm 17 being movable with referenceone to the other by the movement of said gun on its said axis; thetelescope 5 also movable on. a transverse, horizontal axis and supportedin proximity to said gun, shaft 7, intermediate mechanism,

for communicating motion from said shaft to said telescope, drum 18 onsaid shaft 7 carrying the elongated body 19, contact-arm 20 bearing onsaid body 19, a source of electricity, an electrical indicatingapparatus and circuit connections arranged in Wheatstone bridge,substantially as described.

2. In combination with a telescope, 5, a gun and a support, 3, movablebodily With said gun and carrying said telescope 5, the baseplate 22pivoted on saidl support and having .an opening, 37, a fixed pin, 38, onsaid suppqrt in said opening, an abutment, 39, on said base-plate 22, aspring, 40, interposed between said pin 3S and said abutment 39, ascrew, 42, journaled on said base-plate 22 and bearing upon said pin 38,substantially as described.

In combination with a telescope, 5, a gun and a support, 3, movablebodily with said gun, a base-plate, 22, carrying said telescope pivotedon said support and having an opening, 37, a fixed pin, 38, on saidsupport in said opening, an abutment, 39, on said base-plate 22, aspring, 40, interposed between said pin 3S and said abutment 39, ascrew, 42, journaled on said base-plate 22 and bearing upon said pin 3S,and a micrometer-head, 43, on said screw and a fixed mark or index inproximity to said head: the said head being suitably y graduated toenable the telescope to be adj usted in azimuth to compensate fordisplacement of thelprojectile due to the movement of the gun, orsaiddistant object, or both, substantially as described.

4. In combination with a telescope 5, a baseplate, 22, carrying saidtelescope, pivoted on said support and having an opening 37, a pin 38 onsaid support in said opening, an abutment S9 on said base-plate, aspring 40 interposed bet-wcen said pin 3S and said abutment, 39, a screw42 j ournaled on said base-plate and bearingupon said pin 38, amicrometer-head 43 on said screw and a fixed, graduated arc 44 inproximity to said micrometer-head: the

said head 43 being suitably graduated to en-v able the telescope to beadjusted in azimuth to compensate for displacement of its line of sightto a distant object due to the bodily movement of said telescope or saiddistant Object, or both, and the said fixed are 44 being suitablygraduated to allow of adjustment of said telescope in azimuth tocompensate for drift of the projectile thrown from a gun, substantiallyas described.

WM. ARNOUX, JOHN C. SANDERS.

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